rate-limit submissions

[vadosnaprimer]

When you attempt to submit by going from sub list page to SubmitMovie, I replace the entire page with the notice telling how much you need to wait, if you're beyond the limit. The limit is configured in appsettings.

I doubt it's done properly, but should be fixable.

fix #1709

[Masterjun3]

This seems to be only a soft limit, a client limit, right? So for example someone opening 20 tabs of the submission page could still submit them all one after another?

[vadosnaprimer]

Woops...